Composite sheet, multilayer ceramic electronic component, and method for manufacturing the multilayer ceramic electronic component

ABSTRACT

A composite sheet includes a ceramic green sheet having a lengthwise direction and a conductor film printed on the ceramic green sheet. The conductor film has a shape that has a longitudinal dimension extending in the lengthwise direction and a lateral dimension perpendicular or substantially perpendicular to the longitudinal direction. The conductor film includes a plurality of thickness-varied regions arranged in a row or a plurality of rows extending in the lengthwise direction while being dispersed in the lengthwise direction. The thickness-varied regions have a thickness that is different from a thickness of a portion of the conductor film excluding the thickness-varied regions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to composite sheets including a conductorfilm located on a ceramic green sheet, a multilayer ceramic electroniccomponent including the composite sheets, and a method for manufacturingthe multilayer ceramic electronic component.

2. Description of the Related Art

A multilayer ceramic electronic component such as a multilayer ceramiccapacitor has been manufactured thus far in the following manner.Firstly, an internal electrode is printed on a ceramic green sheet toform a composite sheet. Then, multiple composite sheets of this type arebeen stacked on top of one another. As the size of the multilayerceramic electronic components has been reduced, the number of ceramicgreen sheets and internal electrodes to be stacked on top of one anotherhas been increasing. The increase in number of sheets and electrodesrequires a longer time for stacking the sheets and the electrodes on topof one another. If the time for stacking the sheets and the electrodesis reduced, the interlayer adhesion is weakened. If the interlayeradhesion is weakened, layers become more likely to be displaced from oneanother during a stacking step.

International Publication No. WO 2011/071143 discloses a multilayerceramic electronic component that includes internal electrodes eachhaving a saddle portion protruding in the thickness direction at its endportion. These internal electrodes are stacked in such a manner that thesaddle portions do not overlap one another in the thickness direction,whereby delamination is prevented.

As described in International Publication No. WO 2011/071143, thestructure in which each internal electrode includes a saddle portion canprevent delamination from occurring and enhance the adhesion between theinternal electrodes and the ceramic green sheets at theinternal-electrode end portions. The enhancement of the adhesion isconsidered to prevent the electrodes and the sheets from being displacedfrom one another during the stacking step.

However, further size reduction of multilayer ceramic electroniccomponents requires a further enhancement of the adhesion betweeninternal electrodes and ceramic green sheets.

SUMMARY OF THE INVENTION

Accordingly, preferred embodiments of the present invention provide acomposite sheet that has an enhanced adhesion between a conductor filmand a ceramic green sheet so as to be capable of effectively preventingstacking displacement. Other preferred embodiments of the presentinvention provide a multilayer ceramic electronic component that has anenhanced adhesion between ceramic layers and internal electrodes and amethod for manufacturing the multilayer ceramic electronic component.

A composite sheet according to a preferred embodiment of the presentinvention includes a ceramic green sheet having a lengthwise directionand a conductor film printed on the ceramic green sheet. The conductorfilm includes a plurality of thickness-varied regions arranged in a rowextending in the lengthwise direction while being dispersed in thelengthwise direction, the thickness-varied regions have a thickness thatis different from a thickness of a portion of the conductor filmexcluding the thickness-varied regions.

In a composite sheet according to another preferred embodiment of thepresent invention, the thickness-varied regions have a dot shape orsubstantially a dot shape when seen in a plan view.

In a composite sheet according to another preferred embodiment of thepresent invention, the plurality of thickness-varied regions define aplurality of rows.

In a composite sheet according to another preferred embodiment of thepresent invention, the thickness-varied regions are thin regions thathave a smaller thickness than the portion of the conductor filmexcluding the thickness-varied regions.

In a composite sheet according to another preferred embodiment of thepresent invention, the thickness-varied regions are thick regions thathave a larger thickness than the portion of the conductor film excludingthe thickness-varied regions.

In a composite sheet according to another preferred embodiment of thepresent invention, a center thin region that has a smaller thicknessthan the thick regions is provided within the thick regions.

A multilayer ceramic electronic component according to a preferredembodiment of the present invention includes a sintered ceramic compactand a plurality of internal electrodes disposed in the sintered ceramiccompact so as to be stacked on top of one another with ceramic layersinterposed therebetween. At least one of the internal electrodes has aflat or substantially flat shape having a longitudinal direction and alateral direction perpendicular or substantially perpendicular to thelongitudinal direction. The at least one of the internal electrodesincludes a plurality of density-varied regions dispersedly arranged in arow or a plurality of rows extending in the longitudinal direction, thedensity-varied regions have a density different from a density of aportion of the at least one of the internal electrodes excluding thedensity-varied regions.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, the density-variedregions have a dot shape or substantially a dot shape when seen in aplan view.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, the plurality of thedensity-varied regions define a plurality of rows.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, the density-variedregions are low-density regions that have a lower density than theportion of the at least one of the internal electrodes excluding thedensity-varied regions.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, the density-variedregions are high-density regions that have a higher density than theportion of the at least one of the internal electrodes excluding thedensity-varied regions.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, a center low-densityregion that has a lower density than the high-density regions isprovided within the high-density regions.

In a multilayer ceramic electronic component according to anotherpreferred embodiment of the present invention, the multilayer ceramicelectronic component is a multilayer ceramic capacitor.

A method for manufacturing a multilayer ceramic electronic componentaccording to another preferred embodiment of the present inventionincludes a step of preparing a plurality of composite sheets eachaccording to any one of the other preferred embodiments of the presentinvention; a step of stacking the plurality of composite sheets on topof one another to obtain a multilayer body; a step of cutting themultilayer body into multilayer pieces forming individual multilayerceramic electronic components; and a step of sintering the multilayerpieces forming the individual multilayer ceramic electronic componentsto obtain sintered ceramic compacts each including a plurality ofinternal electrodes formed by sintering the conductor films.

In the composite sheets according to various preferred embodiments ofthe present invention, the conductor films include multiplethickness-varied regions arranged in a row or rows extending in thelengthwise direction. Thus, when multiple composite sheets are stackedon top of one another, the composite sheets are effectively preventedfrom being displaced from one another. In addition, the adhesion betweenthe conductor film and the ceramic green sheet is effectively enhanced.

By performing a method for manufacturing a multilayer ceramic electroniccomponent according to various preferred embodiments of the presentinvention using a composite sheet according to various preferredembodiments of the present invention, a multilayer ceramic electroniccomponent according to various preferred embodiments of the presentinvention are provided. Multilayer ceramic electronic componentsaccording to various preferred embodiments of the present inventioneffectively enhance the adhesion between internal electrodes andceramics, and significantly reduce or prevent stacking displacement.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of a composite sheet prepared according to afirst preferred embodiment of the present invention, FIG. 1B is aschematic plan view of a conductor film, and FIG. 1C is an enlargedcross-sectional view of a related portion of the conductor film.

FIG. 2A is a rough perspective view illustrating a photogravure used forprinting a conductor film according to the first preferred embodiment ofthe present invention and FIG. 2B is a schematic plan view illustratinga printing unit of the photogravure.

FIG. 3 is an enlarged cross-sectional view schematically illustratingthe structure of an internal electrode obtained by sintering theconductor film according to the first preferred embodiment of thepresent invention.

FIGS. 4A and 4B are cross-sectional front views respectivelyillustrating first and second composite sheets prepared by the methodfor manufacturing a multilayer ceramic electronic component according tothe first preferred embodiment of the present invention.

FIG. 5 is a schematic front view illustrating a schematic front viewillustrating a mother multilayer body manufactured according to thefirst preferred embodiment of the present invention.

FIG. 6 is a cross-sectional front view illustrating a multilayer ceramiccapacitor defining a non-limiting example of a multilayer ceramicelectronic component according to the first preferred embodiment of thepresent invention.

FIGS. 7A to 7C are partially cutaway, enlarged cross-sectional viewsillustrating a step of transferring a conductive paste from thephotogravure to a ceramic green sheet.

FIG. 8 is a partially cutaway cross-sectional view illustrating a stepof transferring a conductive paste from the photogravure to the ceramicgreen sheet according to another preferred embodiment of the presentinvention.

FIG. 9 is a partially cutaway cross-sectional view illustrating a stepof transferring a conductive paste from the photogravure to the ceramicgreen sheet according to another preferred embodiment of the presentinvention.

FIG. 10 is a schematic plan view illustrating a conductor film accordingto a second preferred embodiment of the present invention.

FIG. 11 is a schematic plan view illustrating a conductor film accordingto a third preferred embodiment of the present invention.

FIG. 12 is a rough plan view illustrating the shape of a printingportion of a photogravure used to form a conductor film according to afourth preferred embodiment of the present invention.

FIG. 13 is a rough plan view illustrating the shape of a printingportion of a photogravure used to form a conductor film according to afifth preferred embodiment of the present invention.

FIG. 14 is a schematic plan view of the structure of a conductor filmaccording to a sixth preferred embodiment of the present invention.

FIG. 15 is a schematic plan view of a printing portion of thephotogravure used to print a conductor film according to the sixthpreferred embodiment.

FIG. 16 is a schematic plan view of a conductor film according to aseventh preferred embodiment of the present invention.

FIG. 17 is a schematic plan view of a conductor film according to aneighth preferred embodiment of the present invention.

FIG. 18 is a plan view of a photogravure used to form a conductor filmaccording to a ninth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the present invention is disclosed belowby describing specific preferred embodiments of the present invention.

First Preferred Embodiment

A first preferred embodiment of the present invention preferably is amultilayer ceramic capacitor, serving as a non-limiting example of amultilayer ceramic electronic component, and a method for manufacturingthe multilayer ceramic capacitor.

In the first preferred embodiment, a photogravure 1 illustrated in FIG.2A is used to form a conductor film by printing. The photogravure 1 isused to print a conductive paste on a ceramic green sheet by aphotogravure process. The photogravure 1 has a cylindrical shape. Thephotogravure 1 is made of appropriate metal such as a stainless steel.

Multiple cells 2 are formed on an outer circumferential surface of thephotogravure 1. Portions of a conductive paste transferred from themultiple cells 2 are connected together to form a single print. Thus, asschematically illustrated in FIG. 2B, a single printing portion 3 thatforms a single print includes multiple cells 2.

Each cell 2 is a recess formed in a surface 1 a of the photogravure 1. Aportion between pairs of adjacent recesses defines and functions as abank 1 b that separates the adjacent cells 2 from each other.

Here, as will be described below, the multiple cells 2 do notnecessarily have to be completely separated from each other by the bank.

In the first preferred embodiment, first composite sheets 11 illustratedin FIG. 4A and second composite sheets 12 illustrated in FIG. 4B areprepared. The first composite sheets 11 are formed by printing multipleconductor films 14 on a mother ceramic green sheet 13 using thephotogravure 1.

Ceramic materials for the ceramic green sheet 13 are not particularlylimited. Examples usable as the ceramic materials include dielectricceramics mainly composed of materials such as BaTiO₃, CaTiO₃, SrTiO₃, orCaZrO₃. In the case where a component such as a multilayer ceramicpiezoelectric device or a multilayer ceramic inductor is formed as amultilayer ceramic electronic component, materials such as piezoelectricceramics or magnetic ceramics may be used in accordance with thefunctions of the component.

As illustrated in FIG. 1A, multiple conductor films 14 are arranged in amatrix on a ceramic green sheet 13.

Also in the second composite sheet 12 illustrated in FIG. 4B, multipleconductor films 15 are printed on a mother ceramic green sheet 13. Themultiple conductor films 15 are made of the same material as andarranged in the same manner as the multiple conductor films 14.

One of the unique features of the present preferred embodiment is thatthe conductor films 14 and the conductor films 15 each have a uniquethickness distribution. Referring now to FIGS. 1B and 1C, thisdistribution is described using a conductor film 14 as an example.

The conductor film 14 is formed by using one printing portion 3illustrated in FIG. 2B. Specifically, multiple cells 2 in one printingportion 3 are filled with portions of a conductive paste. These portionsof the conductive paste are transferred and connected together, so thata single conductor film 14 is formed.

The ceramic green sheet 13 illustrated in FIG. 1A is a long ceramicgreen sheet. The direction of the length is defined as a lengthwisedirection L. The direction perpendicular to the lengthwise direction Lis defined as a widthwise direction W.

As illustrated in FIG. 1A, in the composite sheet 11, multiple conductorfilms 14 are arranged in a matrix along the lengthwise direction L andthe widthwise direction W. Each conductor film 14 preferably has arectangular or substantially rectangular shape having a lengthwisedirection and a widthwise direction. The lengthwise direction of theconductor film 14 is defined as the same direction as the lengthwisedirection L.

FIG. 1B is a plan view schematically illustrating the thicknessdistribution of a single conductor film 14. In FIG. 1B, a region of theconductor film 14 having the largest thickness is cross-hatched. Withina first region 14 a of the conductor film 14, which is the cross-hatchedregion, multiple dot-shaped second regions 14 b are provided. Eachsecond region 14 b includes a thin portion 14 d, which has a smallerthickness than the first region 14 a, at its center portion. Aring-shaped region extending from the outer circumference of the thinportion 14 d to the first region 14 a is defined as a thicknesstransition region 14 c. Each second region 14 b is a thin region havinga smaller thickness than the first region 14 a and corresponds to athickness-varied region according to a preferred embodiment of thepresent invention.

The multiple dot-shaped second regions 14 b are dispersed over theconductor film 14 in the lengthwise direction. In other words, themultiple dot-shaped second regions 14 b define rows extending in thelengthwise direction. In this preferred embodiment, the number of rowspreferably is three, for example. Here, the multiple second regions 14 bon both side rows in the widthwise direction are arranged alternatelywith the multiple second regions 14 b on the middle row in the widthwisedirection.

FIG. 1C is an enlarged cross-sectional view illustrating a portion inwhich a pair of adjacent second regions 14 b of the conductor film 14are located.

It should be noted that the thickness distribution of the conductorfilms 14 and 15 is not illustrated in FIGS. 4A and 4B, sinceillustration of the thickness distribution is difficult in FIGS. 4A and4B.

In the present preferred embodiment, the first composite sheets 11 andthe second composite sheet 12 are alternately stacked on top of oneanother. The first composite sheets 11 and the second composite sheets12 are stacked in such a manner that each conductor film 15 on the upperside in the stacking direction is located between a pair of adjacentconductor films 14 of the first composite sheet 11 on the lower side inthe stacking direction.

Subsequently, an appropriate number of unprinted ceramic green sheetsare disposed above and below the stacked sheets to define a multilayerbody. This multilayer body is pressure-bonded in the thickness directionto define a mother multilayer body 16 illustrated in FIG. 5.

In the mother multilayer body 16, the stacked composite sheets 11 and 12are caused to firmly adhere to one another by the pressure bonding.Particularly, the conductor films 14 and 15 having the above-describedthickness distribution effectively enhance the adhesion between thecomposite sheets 11 and 12. This structure also effectively prevents thecomposite sheets 11 and 12 from being displaced from each other duringthe stacking step. When the conductor films 14 are taken as examples,since each conductor film 14 includes dot-shaped second regions 14 bwhose thickness is different from the remaining region, as describedabove, the conductor films 14 are caused to firmly adhere to the ceramicgreen sheet 13 of a composite sheet 12 stacked on top of the conductorfilms 14 by the pressure bonding. In the same manner, each conductorfilm 15 is caused to firmly adhere to the ceramic green sheet 13 of acomposite sheet 11 stacked on the conductor films 15. Thus, the adhesionbetween the conductor films 14 or 15 and the ceramic green sheets 13 isgreatly enhanced. Moreover, at the stacking of layers, the displacementof layers in the directions perpendicular or substantially perpendicularto the stacking direction, that is, stacking displacement is effectivelyprevented.

The method for forming conductor films 14 and 15 having theabove-described thickness distribution is described below in detail.

Subsequently, the mother multilayer body 16 is cut in the thicknessdirection as indicated by broken lines B in FIG. 5 to obtain multilayerpieces defining individual multilayer ceramic capacitors. Thesemultilayer pieces defining individual multilayer ceramic capacitors aresintered, such that sintered ceramic compacts 17, one of which isillustrated in FIG. 6, are obtained.

In each sintered ceramic compact 17, first internal electrodes 14A andsecond internal electrodes 15A are alternately stacked on top of oneanother with ceramic layers interposed therebetween. Each first internalelectrode 14A is a section of the first conductor film 14. Each secondinternal electrode 15A is a section of the second conductor film 15.

Multiple first internal electrodes 14A are drawn out to a first endsurface 17 a. Multiple second internal electrodes 15A are drawn out to asecond end surface 17 b, opposite to the first end surface 17 a. Firstand second external electrodes 18 and 19 are formed so as torespectively cover the first and second end surfaces 17 a and 17 b.Consequently, a multilayer ceramic capacitor 20 is obtained.

The first and second external electrodes 18 and 19 can be formed by anyappropriate method such as applying and sintering a conductive paste,for example.

In the multilayer ceramic capacitor 20 thus obtained, the adhesionbetween the conductor films 14 or 15 and the ceramic green sheets 13 hasalready been enhanced at the stage of the mother multilayer body 16 andstacking displacement is less likely to occur. Thus, also in theobtained sintered ceramic compact 17, the adhesion between the first orsecond internal electrodes 14A or 15A and the ceramic layers has beeneffectively enhanced, so that delamination is less likely to occur.Since the stacking displacement is also prevented, a multilayer ceramiccapacitor 20 having desired characteristics is easily and reliablyprovided.

In the first internal electrodes 14A and the second internal electrodes15A thus obtained by sintering, the density of conductive particles thatform the internal electrodes has a distribution according to thethickness distribution at the stage of the conductor films 14 and 15.This density distribution is described referring to FIG. 3. FIG. 3 is anenlarged cross-sectional view schematically illustrating a cross sectionof a first internal electrode 14A subjected to sintering. In the firstinternal electrode 14A, a large number of conductive particles 21 areattached together by sintering. Gaps are formed at portions indicated byarrows B1, B2, and B3. Although not illustrated, other conductiveparticles are disposed at the main side and oblique sides of each gap.Portions around the gaps have a relatively low density of conductiveparticles 21 and define low-density regions. Portions around thelow-density regions are defined as high-density regions in which a largenumber of conductive particles 21 exist.

The high-density regions are defined by the above-described firstregions 14 a of the conductor film 14. On the other hand, theabove-described dot-shaped second regions 14 b define the low-densityregions. This is because, when a conductor film 14 having theabove-described thickness distribution is sintered, thin portions becomelow-density regions in which the density of conductive particles in theinternal electrode formed by sintered is low, while thick portionsbecome high-density regions in which the density of conductive particlesin the internal electrode is high.

The first and second internal electrodes 14A and 15A of the obtainedmultilayer ceramic capacitor 20 thus have low-density regions, whichdefine and serve as multiple density-varied regions arranged in rows inthe lengthwise direction. Here, the lengthwise direction corresponds tothe direction connecting the first end surface 17 a and the second endsurface 17 b together.

In the conductor film 14 illustrated in FIG. 1B, for example, three rowsof multiple second regions 14 b are preferably provided in parallel orsubstantially in parallel in the widthwise direction. In the multilayerceramic capacitor 20 thus obtained, for example, three rows of multiplelow-density regions extending in the lengthwise direction are preferablyprovided in parallel or substantially in parallel in the widthwisedirection.

Experiments conducted by the inventors of this application proved thatthe low-density regions and the high-density regions can be reliablyformed in the internal electrodes 14A and 15A under the conditions wherethe conductor films 14 and 15 before sintering have a thickness withinthe range of about 0.3 μm to about 1.2 μm, for example, at first regionsand a thickness within a range of about 80% to about 99%, for example,of the thickness of the first regions at thin portions of secondregions. As described above, in this preferred embodiment, the particlediameter of the conductive particles in the conductive paste preparedfor forming the first regions and the dot-shaped second regionsincluding thin regions is preferably about 0.4 μm or smaller, forexample. In this preferred embodiment, the conductive particlespreferably have a particle diameter on the order of about 0.3 μm, forexample. In this manner, the conductor films 14 and 15 according to thepresent preferred embodiment that are thinner and have thicknessdistribution is easily formed.

In this preferred embodiment, the low-density regions are provided inthe internal electrodes 14A and 15A to define and serve asdensity-varied regions. However, the density-varied regions do notnecessarily have to be areas that have a relatively low density. As willbe clear from other preferred embodiments described below, thedensity-varied regions may be high-density regions that have a higherdensity than other portions. Alternatively, a center low-density regionthat has a lower density than the high-density region may be providedwithin the high-density region.

Referring now to FIG. 7A to FIG. 9, a non-limiting example of a methodfor forming the conductor film 14 is described.

FIGS. 7A to 7C are partially enlarged cross-sectional views illustratinga step of forming existing conductor films having a uniform orsubstantially uniform thickness without second regions. As illustratedin FIG. 7A, multiple cells 2 are formed on the surface of a photogravure1. A portion between adjacent cells 2 defines and serves as a bank 1 b.A portion of a conductive paste 101 is distributed to each cell 2. Aceramic green sheet 102 is brought into contact with the surface of thephotogravure 1 with pressure. Consequently, the portions of theconductive paste 101 are transferred to one side of the ceramic greensheet 102. Here, the conductive paste 101 has fluidity. Thus, theconductive paste 101 gradually moves from the banks 1 b to regions eachbetween adjacent banks 1 b, from the state illustrated in FIG. 7A to thestate illustrated in FIG. 7B. Specifically, as illustrated in FIG. 7B,the conductive paste 101 moves over one surface of the ceramic greensheet 102 so as to spread outward from the banks 1 b.

As illustrated in FIG. 7C, as time passes, the conductive paste 101spreads over the surface of the ceramic green sheet 102 and has auniform or substantially uniform thickness. When the composite sheetthus obtained is sintered, an electrode having a uniform orsubstantially uniform film thickness can be formed.

However, in the case where conductor films having a uniform orsubstantially uniform thickness are used, the adhesion between theconductor films and the ceramic green sheets stacked on the conductorfilms may not be sufficiently high. This structure can thus causestacking displacement, as described above.

In this preferred embodiment on the other hand, as illustrated in FIG.8, a portion of a conductive paste 14 x distributed to a cell 2 istransferred to one surface of the ceramic green sheet 13 along the banks1 b as indicated by arrows E. Then, the conductive paste 14 x startsspreading in directions away from the banks 1 b as in the caseillustrated in FIG. 7B. Unlike the existing case, in the presentpreferred embodiment, the ceramic green sheet 13 is separated from thephotogravure 1 at the state illustrated in FIG. 8. In other words, theconductive paste 14 x can have thickness distribution by increasing theprinting speed by approximately 10 mm/min to about 30 mm/min, forexample, to accelerate separation of the ceramic green sheet 13 from thephotogravure 1.

Instead of accelerating separation of the ceramic green sheet 13 fromthe photogravure 1, the fluidity of the conductive paste 14 x may beadjusted to cause the conductive paste 14 x to have the desiredthickness distribution. Specifically, a conductive paste having a lowfluidity and such a composition that the film thickness is less likelyto be immediately uniformed as illustrated in FIG. 7C may be used as theconductive paste 14 x. Alternatively, accelerating separation of theceramic green sheet 13 from the photogravure 1 and adjusting thefluidity of the conductive paste may both be used.

Moreover, the particle diameter of conductive particles contained in theconductive paste 14 x is preferably small. The use of small diameterparticles enhances the viscosity of the conductive paste 14 x andreduces the fluidity. Preferably, the particle diameter of conductiveparticles is about 0.4 μm or smaller, for example. Thus, the conductivepaste 14 x is reliably and easily provided with the thicknessdistribution.

To form thin regions in the conductor film 14 as in the case of thepresent preferred embodiment, a gap between adjacent banks 1 b, that is,a width G of a cell 2 is desirably increased. In this way, thin portionsare easily formed in the conductive paste 14 x.

By contrast, dot-shaped thick regions preferably are formed on theconductor film. In this case, in order to form thick regions, thedimension of the bank 1 b in the widthwise direction may be increasedand the distance between adjacent banks 1 b, that is, the width G of acell may be narrowed.

In the case where a center thin region is formed in each of dot-shapedthick regions as will be described below, the width G of the cell 2 andthe width F of the bank 1 b may both be increased.

By increasing the distance between adjacent banks 1 b as illustrated inFIG. 9, a center thin portion H is preferably formed at a center portionof each dot-shaped region on the ceramic green sheet 13. Specifically, acenter thin portion H is preferably formed at the center of the thickportion.

The thickness distribution of the conductor film 14 formed on theceramic green sheet 13 in the above-described manner can be perceived byobserving transmitted light. Specifically, the thick portions and thethin portions can be perceived by measuring the intensity of transmittedlight. Thus, the thickness distribution and the shape of the conductorfilm formed on the ceramic green sheet can be optically perceived.

The thickness distribution of internal electrodes in a finally obtainedmultilayer ceramic electronic component may be perceived in thefollowing manner. A sintered compact is ground until internal electrodesare exposed. After the internal electrodes are exposed, the sinteredceramic compact is immersed in a potassium hydroxide solution and avoltage is applied to the compact. The application of the voltage causesdelamination. The delaminated sample is observed by a microscope or thelike to perceive the density distribution of conductive particles in across section of the internal electrodes. In other words, whether or notthe internal electrodes include a high density portion or a low densityportion can be perceived visually or through an image processing device.

The thickness distribution of the conductor films can be perceived bymeasuring the surface state with a contact or contactless roughnessmeasuring device.

Second Preferred Embodiment to Ninth Preferred Embodiment

Composite sheets according to the present invention are not limited tothe composite sheets 11 and 12 according to the first preferredembodiment.

FIG. 10 is a schematic plan view illustrating the thickness distributionof a conductor film on a composite sheet according to a second preferredembodiment of the present invention. In the second preferred embodiment,a conductor film preferably has a rectangular or substantiallyrectangular shape having a lengthwise direction and a widthwisedirection. In third and subsequent preferred embodiments describedbelow, conductor films preferably have a rectangular or substantiallyrectangular shape having a lengthwise direction that is parallel orsubstantially parallel to the lengthwise direction of theabove-described ceramic green sheet 13.

In the illustration of the second to ninth preferred embodiments, as inthe case of the first preferred embodiment, portions of a conductor filmhaving the smallest thickness are not hatched, portions of the conductorfilm having the second smallest thickness are hatched with obliquelines, and portions of the conductor film having the largest thicknessare cross-hatched.

As illustrated in FIG. 10, dot-shaped second regions 33 are arranged inrows extending in the lengthwise direction in a conductor film 31. Alsoin this preferred embodiment, three rows of dot-shaped regions 33extending in the lengthwise direction are preferably provided inparallel or substantially in parallel in the lateral direction, forexample. Portions other than the dot-shaped second regions 33 are thefirst regions 32, which are not hatched.

In this preferred embodiment, the first regions 32 have the smallestthickness. On the other hand, the dot-shaped second regions 33 have alarger thickness than the first regions 32 and define and serve as thickregions. In addition, each second region 33 has a circular orsubstantially circular thick region 33 b having the largest thickness ata center portion and a ring-shaped thickness transition region 33 a,which is a portion extending from the outer circumference of the thickregion 33 b to the first region 32. As in the case of this preferredembodiment, the dot-shaped second regions 33 defining and serving asthickness-varied regions may be thick regions that have a largerthickness than the first regions 32. In order to obtain the thicknessdistribution as in the case of this preferred embodiment, the bank widthis preferably set at about 10 μm to about 20 μm and the distance betweenadjacent banks is preferably set at about 30 μm to about 200 μm, forexample.

FIG. 11 is a schematic plan view of a conductor film 34 according to athird preferred embodiment of the present invention. In the conductorfilm 34, as in the case of the second preferred embodiment, rows ofdot-shaped second regions 35 extending in the lengthwise direction areprovided within the first regions 32 having the smallest thickness. Alsoin this preferred embodiment, three rows are preferably provided inparallel or substantially in parallel in the lateral direction, forexample.

The third preferred embodiment is different from the second preferredembodiment with regard to the point that a circular center thin region33 d is provided at a center portion of each thick region 33 b definingand serving as a thickness-varied region. A ring-shaped thicknesstransition region 33 c extends from the outer circumference of thecenter thin region 33 d to the thick region 33 b. In this manner, thecenter thin region 33 d is preferably provided within the thick region33 b. In order to obtain the thickness distribution as in the case ofthis preferred embodiment, the bank width is preferably set at about 3μm to about 20 μm and the distance between banks that sandwich the cellfrom both sides is preferably set at about 80 μm to about 200 μm, forexample.

The patterns of cells on the photogravures used for printing conductorfilms 14, 31, and 34 according to the first to third preferredembodiments can be appropriately modified. For example, in a fourthpreferred embodiment illustrated in FIG. 12, multiple hexagonal cells 41are arranged on the surface of a photogravure 1 in a row in thelengthwise direction with banks 42 interposed therebetween in order toform a rectangular or substantially rectangular print. Each bank 42surrounds a hexagonal cell 41. In addition, ribs 42 a extend in thelateral direction toward the long sides of a printing portion 3 fromboth ends of the bank 42 in the lateral direction, the bank 42surrounding a cell 41 in the middle row. Each rib 42 a is disposed so asto surround a halved-hexagonal shape together with portions of the banks42 and another rib 42 a that is adjacent to the rib 42 a in thelengthwise direction in the printing portion 3.

In other words, the cell pattern in the printing portion 3 has a shapesuch that a structure in which multiple hexagonal cells 41 arealternately arranged is cut in such a manner that outer halves of cellson both sides in the lateral direction are cut off while leaving onlythe cells 41 in the middle row uncut.

Here, the end of each rib 42 a is separated from the long side of theprinting portion 3 by a gap 43. This gap 43 may be omitted.

Although FIG. 12 illustrates a cell pattern that includes hexagonalcells 41, banks 52 may be arranged so as to surround rectangular orsubstantially rectangular cells 51, as in a fifth preferred embodimentillustrated in FIG. 13. Also in this preferred embodiment, multiplerectangular or substantially rectangular cells 51 are arranged in rowsin the lengthwise direction L. Each bank 52 is arranged so as tosurround a cell 51. Ribs 52 a are formed toward the long sides of thephotogravure 1 from middle portions of sides of each bank 52 that areparallel or substantially parallel to the long sides of thephotogravure. Thus, rows of multiple rectangular or substantiallyrectangular cells 51 are similarly arranged on both sides, in thelateral direction, of a middle row of cells 51 so as to extend in thelengthwise direction.

Also in FIG. 13, as in the case illustrated in FIG. 12, the cells 51arranged in the middle row and multiple cells 51 arranged on both sidesin the lateral direction are alternately arranged.

FIG. 14 is a schematic plan view illustrating a conductor film 61according to a sixth preferred embodiment of the present invention. Asin the case of the second preferred embodiment, in the illustration ofthe conductor film 61, regions that have the smallest thickness are nothatched, regions that have the second smallest thickness are hatchedwith oblique lines, and a region having the largest thickness iscross-hatched. Here, the conductor film 61 includes multiple dot-shapedsecond regions 62 arranged in rows in the lengthwise direction. As inthe case of the first preferred embodiment, each of the dot-shapedsecond regions 62 includes a circular or substantially circular thinregion 62 b at a center portion and a ring-shaped thickness transitionregion 62 a around the thin region 62 b. The remaining region definesand serves as a first region 62 c. The first region 62 c is a regionhaving the largest thickness.

The conductor film 61 according to this preferred embodiment isdifferent from the conductor film according to the first preferredembodiment with regard to the point that the dot-shaped second regions62 are arranged in two rows in parallel or substantially in parallel inthe lateral direction, instead of three rows. In this manner, the numberof rows of dot-shaped regions arranged in the lengthwise direction isnot limited to three in the present invention and may be two or anotherappropriate number that is four or larger, for example.

FIG. 15 is a schematic plan view illustrating an example of a cellpattern used to obtain the conductor film 61 according to this preferredembodiment. Here, multiple cells 63 having a halved-hexagonal shape arearranged in the lengthwise direction while being separated from oneanother by banks 64. These cells 63 preferably are arranged in two rowsin parallel or substantially in parallel in the lateral direction, forexample.

FIG. 16 is a schematic plan view of a conductor film 71 according to aseventh preferred embodiment. The conductor film 71 according to theseventh preferred embodiment is the same as the conductor film 14according to the first preferred embodiment except for the arrangementof dot-shaped second regions. The same portions are thus denoted by thesame reference numerals. Multiple dot-shaped second regions 14 b areprovided within a first region 14 a. Each second region 14 b includes acircular or substantially circular thin region 14 d at a center portionand a ring-shaped thickness transition region 14 c that extends from theouter circumference of the thin region 14 d to the first region 14 awhile changing its thickness. The seventh preferred embodiment isdifferent from the first preferred embodiment in that the multiplesecond regions 14 b are arranged in a matrix, instead of alternately.Specifically, as indicated by thin lines G in FIG. 16, second regions 14b that belong to different rows are arranged side by side in the lateraldirection.

In this manner, the second regions 14 b may be arranged in a matrixinstead of alternately.

FIG. 17 is a schematic plan view of a conductor film according to aneighth preferred embodiment. As in the case of the conductor film 71according to the seventh preferred embodiment, the conductor film 81according to the eighth preferred embodiment includes multipledot-shaped second regions 14 b arranged in rows adjacent to the longsides of the conductor film 81. In place of the middle row illustratedin FIG. 16, a zigzag thin region 82 having a small thickness is arrangedso as to extend in the lengthwise direction. In this manner, the thinregion 82 preferably has a zigzag shape so as to extend in thelengthwise direction. Thus, the adhesion between the conductor film 81and the ceramic green sheet is enhanced further.

FIG. 18 is a schematic plan view illustrating a cell pattern 91 on aphotogravure used in a ninth preferred embodiment. The cell pattern 91includes multiple rectangular or substantially rectangular cells 92arranged in a matrix. Specifically, multiple cells 92 are separated fromone another with banks 93 and 94 interposed therebetween. The multiplecells 92 are preferably arranged in three rows so as to extend in thelengthwise direction, for example. The multiple cells 92 are arranged ina matrix. Here, L-shaped banks 93 and I-shaped banks 94 preferably areappropriately combined to define the cells 92. For example, by using thecell pattern on the photogravure used in the ninth preferred embodiment,the conductor film according to the eighth preferred embodiment can beobtained. In order to obtain the conductor film according to the eighthpreferred embodiment, the length of a cut-out portion of the bank 93 inwhich a portion of the bank 93 is cut out such that adjacent cells 92separate from each other while allowing the cells 92 to be continuouswith each other is preferably about 50% to about 80% of the distancebetween banks on both sides of a cell, for example.

As is clear from the second to ninth preferred embodiments, the cellpattern on the photogravure and the arrangement pattern of the thinregions and the thick regions on the conductor film can be modified invarious manners in the present invention and these patterns are notlimited to those according to the preferred embodiments illustrated.

The above-described preferred embodiments have described a multilayerceramic capacitor and a method for manufacturing the multilayer ceramiccapacitor merely as non-limiting examples. The present invention,however, is applicable to various types of multilayer ceramic electroniccomponents including multilayer ceramic piezoelectric components,multilayer ceramic inductors, or multilayer ceramic substrates, and amethod for manufacturing the same, other than the multilayer ceramiccapacitor and the method for manufacturing the multilayer ceramiccapacitor.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A composite sheet, comprising: a ceramic greensheet having a lengthwise dimension extending in a lengthwise direction;and a conductor film printed on the ceramic green sheet; wherein theconductor film includes a plurality of thickness-varied regions arrangedin a row extending along the lengthwise direction while being dispersedin the lengthwise direction, the thickness-varied regions have athickness that is different from a thickness of a portion of theconductor film excluding the thickness-varied regions.
 2. The compositesheet according to claim 1, wherein the thickness-varied regions have adot shape or substantially a dot shape when seen in a plan view.
 3. Thecomposite sheet according to claim 1, wherein the plurality ofthickness-varied regions define a plurality of rows.
 4. The compositesheet according to claim 1, wherein the thickness-varied regions arethin regions that have a smaller thickness than the portion of theconductor film excluding the thickness-varied regions.
 5. The compositesheet according to claim 1, wherein the thickness-varied regions arethick regions that have a larger thickness than the portion of theconductor film excluding the thickness-varied regions.
 6. The compositesheet according to claim 5, wherein a center thin region that has asmaller thickness than the thick regions is provided within the thickregions.
 7. A multilayer ceramic electronic component, comprising: asintered ceramic compact; and a plurality of internal electrodesdisposed in the sintered ceramic compact so as to be stacked on top ofone another with ceramic layers interposed therebetween; wherein atleast one of the internal electrodes has a flat shape or a substantiallyflat shape having a longitudinal dimension extending in a longitudinaldirection and a lateral dimension extending in a lateral directionperpendicular or substantially perpendicular to the longitudinaldirection; the at least one of the internal electrodes includes aplurality of density-varied regions dispersedly arranged in a rowextending in the longitudinal direction, and the density-varied regionshave a density different from a density of a portion of said at leastone of the internal electrodes excluding the density-varied regions. 8.The multilayer ceramic electronic component according to claim 7,wherein the density-varied regions have a dot shape or substantially adot shape when seen in a plan view.
 9. The multilayer ceramic electroniccomponent according to claim 7, wherein the plurality of thedensity-varied regions define a plurality of rows.
 10. The multilayerceramic electronic component according to claim 7, wherein thedensity-varied regions are low-density regions that have a lower densitythan the portion of the at least one of the internal electrodesexcluding the density-varied regions.
 11. The multilayer ceramicelectronic component according to claim 7, wherein the density-variedregions are high-density regions that have a higher density than theportion of the at least one of the internal electrodes excluding thedensity-varied regions.
 12. The multilayer ceramic electronic componentaccording to claim 11, wherein a center low-density region that has alower density than the high-density regions is provided within thehigh-density regions.
 13. The multilayer ceramic electronic componentaccording to claim 7, wherein the multilayer ceramic electroniccomponent is a multilayer ceramic capacitor.
 14. A method formanufacturing a multilayer ceramic electronic component, comprising: astep of preparing a plurality of composite sheets each according toclaim 1; a step of stacking the plurality of composite sheets on top ofone another to obtain a multilayer body; a step of cutting themultilayer body into multilayer pieces forming individual multilayerceramic electronic components; and a step of sintering the multilayerpieces forming the individual multilayer ceramic electronic componentsto obtain sintered ceramic compacts each including a plurality ofinternal electrodes formed by sintering the conductor films.
 15. Themethod according to claim 14, wherein the multilayer ceramic electroniccomponent is a multilayer ceramic capacitor.
 16. The method according toclaim 14, wherein the thickness-varied regions have a dot shape orsubstantially a dot shape when seen in a plan view.
 17. The methodaccording to claim 14, wherein the plurality of thickness-varied regionsdefine a plurality of rows.
 18. The method according to claim 14,wherein the thickness-varied regions are thin regions that have asmaller thickness than the portion of the conductor film excluding thethickness-varied regions.
 19. The method according to claim 14, whereinthe thickness-varied regions are thick regions that have a largerthickness than the portion of the conductor film excluding thethickness-varied regions.
 20. The method according to claim 19, whereina center thin region that has a smaller thickness than the thick regionsis provided within the thick regions.